Postretirement Plans - Schedule of Changes in the Benefit Obligation, Plan Assets and Funded Status of Pensions and OPB (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Accrued pension plan liability, net	$ (4,287)	$ (5,997)
Pension
Change in benefit obligation
Beginning balance	50,421	54,325
Service cost	9	5	$ 2
Interest cost	2,676	2,635	2,820
Amendments	6	140
Actuarial loss/(gain)	1,501	(2,493)
Gross benefits paid	(4,507)	(4,173)
Subsidies
Spirit Acquisition	1,309
Exchange rate adjustment	10	(18)
Ending balance	51,425	50,421	54,325
Change in plan assets
Beginning balance at fair value	45,574	48,891
Actual return on plan assets	4,562	738
Plan participants’ contributions
Spirit Acquisition	1,362
Benefits paid	(4,367)	(4,034)
Exchange rate adjustment	16	(21)
Ending balance at fair value	47,147	45,574	48,891
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Other assets	145	1,289
Accrued liabilities	(136)	(139)
Accrued retiree health care
Accrued pension plan liability, net	(4,287)	(5,997)
Net amount recognized	(4,278)	(4,847)
Other Postretirement Benefits
Change in benefit obligation
Beginning balance	2,651	2,651
Service cost	51	51	49
Interest cost	135	124	148
Amendments
Actuarial loss/(gain)	(26)	156
Gross benefits paid	(331)	(336)
Subsidies	15	8
Spirit Acquisition	30
Exchange rate adjustment	2	(3)
Ending balance	2,527	2,651	2,651
Change in plan assets
Beginning balance at fair value	183	163
Actual return on plan assets	24	22
Plan participants’ contributions	1	1
Spirit Acquisition
Benefits paid	(2)	(3)
Exchange rate adjustment
Ending balance at fair value	206	183	$ 163
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position [Abstract]
Other assets	76	21
Accrued liabilities	(306)	(313)
Accrued retiree health care	(2,091)	(2,176)
Accrued pension plan liability, net
Net amount recognized	$ (2,321)	$ (2,468)